This invention relates to the manufacture of semiconductor devices with a high surface topography, in particular for the integration of features like MEMS sensors or TSVs.
FR 2 823 865 A1 describes a photolithography method for the application to a substrate having a high surface topography. A planar dry film is applied to the entire substrate surface to cover the open recesses and holes of the substrate. The dry film is subsequently structured to leave only portions of the dry film that close the recesses and holes. The surface topography is thus reduced to allow the areas that are not covered by the remaining portions of the dry film to be subjected to a conventional photolithography.
Mask layers are applied as planar layers continuously covering holes in the substrate or as a lining of sidewalls and bottoms of trenches. Conventional processes for producing the different kinds of mask layers are vacuum-coating and spray-coating, for example. Another method consists of laminating a dry film over the holes, thus forming closed cavities. Gas, especially ambient air, is trapped in the cavities under the environmental conditions prevailing at the time the mask layer is applied. For instance, the gas may have the pressure of an atmosphere under which an etching step is performed. After further process steps the gas pressure in the cavity may exceed the outer pressure, and ruptures in the mask layer may result.